Pamuk, Rushdie protest Turkey's Twitter ban

3/28/14 5:43 AM EDT

Orhan Pamuk, Salman Rushdie and a host of international authors have signed a joint letter from the international writers group PEN protesting the Turkish government's ban on Twitter.

The group, which also includes Zadie Smith and Günter Grass, calls the ban "an unacceptable violation of the right to freedom of speech".

Turkish Prime Minister Recep Tayyip Erdogan restricted access to Twitter last week after some users posted audio recordings that pointed to corruption among the country's top public officials. On Thursday, local news outlets reported that the government had also shut down YouTube.